As demands for processing high-quality moving images increase, a high-capacity data storage optical disk is required. Consequently, high-density rewritable optical recording medium that can record and store high quality video and audio data for many hours is brought to the market, recently.
Examples of the high-density rewritable optical recording medium include a blue lay disk (BD), a high definition digital versatile disk (HD-DVD), etc. The DVD has an about 4.7 GB recording capacity and the BD has an about 25 GB recording capacity. After the BD standard has been introduced, the next generation high density/ultra miniature optical storage device has been developed. Examples of the next generation high density/ultra miniature optical storage device include technologies such as a super-lens, holography, near field recording, etc.
Recently, because these optical storage devices (e.g., compact disk (CD), DVD, BD, HD-DVD) are widely distributed, a home or office of company keeps several tens to hundreds of optical storage disks containing various contents.
FIG. 1 is a block diagram of a structure of a related art optical disk drive.
The related art optical disk drive includes an optical disk 21, a pick-up unit 11, a servo unit 12, a signal processing unit 14, a memory 15, and a micom 13. The optical disk 21 is a recording medium on which data are recorded, reproduced, and erased by a laser. The pick-up unit 11 records/reproduces management information including data recorded on the optical disk 21. The servo unit 12 controls operations of the pick-up unit 11. The signal processing unit 14 demodulates a reproduction signal received from the pick-up unit 11 into a desired signal value, or modulates a signal to be recorded into a signal having a form necessary for performing a recording operation on the optical disk 21 to transmit the signal. The memory 15 stores various information necessary for reproducing the optical disk 21. The micom 13 controls operations of the above components. The components form a recording/reproducing unit 10.
The pick-up unit 11 includes a laser light source such as a laser diode, a collimator lens, an objective lens driven by a focus actuator or a tracking actuator, a polarized beam splitter, an optical component such as a cylindrical lens, a photodetector converting light into an electrical signal, and a front monitor diode monitoring a laser output during a recording or reproducing operation.
The micom 13 detects reflected light from the optical disk 21, and calculates an amount of the reflected light through the detected reflected light to generate a radio frequency (RF) signal representing a total sum of the reflected light with respect to each area of photodiodes. Additionally, the micom 13 generates a focus error signal FE, which is a signal detecting an out-of-focus laser illuminated by the pick-up unit 11 through an astigmatism method. Additionally, the micom 13 generates a tracking error signal TE detecting an out-of-track laser illuminated by the pick-up unit 11 through a push-pull method.
The memory 15 stores various information necessary for reproducing the optical disk 21 and typically includes a random access memory (RAM) and a read only memory (ROM) to store a control program, a theoretical length of each pit and land, or existence probability in combination of each pit and land.
A controller 23 is responsible for controlling entire components.
A decoder 22 finally decodes output data in response to control of the controller 23 and then provides the decoded data to a user.
To record user desired data on a recoding medium, an encoder 24 converts an input signal into a signal of a predetermined format, e.g., a motion picture experts group 2 (MPEG2) transport stream, and then provides the converted signal to the signal processing unit 14 in response to control of the controller 23.
As described above, FIG. 1 illustrates components of recording and reproducing units of the related art optical disk drive. In relation to the reproducing of the optical disk, the optical disk 21, the recording/reproducing unit 10, and the decoder 22 are used. In relation to the recording of the optical disk, the recoding/reproducing unit 10, and the decoder 22 are used in response to control of the controller 23.
Since the optical disk drive reproduces/executes only the contents stored on the optical disk 21, there is inconvenience that the optical disk 21 should be replaced with a new optical disk when a user intends to execute other contents.
Also, since the capacity of the optical disk is limited, the optical disk cannot satisfy the demand of a user who desires to receive a great amount of contents.
Also, since a security method for an optical storage device is not sufficiently provided, data loss due to external trespass emerges as a serious limitation.